Ischemic stroke is now the most frequent cause of persistent neurologic disability in the US. Despite considerable effort there are no therapies that can reduce injury or restore function once a stroke occurs. Over the past several years, our view of stroke as a neuronal disease has been transformed into the concept of stroke as a neurovascular disease, and more recently into the novel theory that stroke is truly a systemic disease in which peripheral inflammatory processes play a fundamental role. This peripheral immune response is a target for stroke therapy, as reducing peripheral infiltration of circulating leukocytes, specifically monocytes and neutrophils, decreases ischemic injury. Transforming growth factor ? activated kinase-1 (TAK1), a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family has been recently recognized as an indispensible signaling molecule in the innate immune response to brain injury. The proposed work will examine the effects of loss of TAK signaling on post-stroke inflammation using selective deletion of TAK in myeloid cells. Mechanistic studies will be performed in TAK1 knockout animals (Aim 1). We will then determine the neuroprotective efficacy of pharmacologically inhibiting TAK in aged mice, a clinically relevant animal model for stroke (Aim 2). These exploratory studies will hopefully identify new biological targets for therapeutic intervention for patients with stroke.